Strain insulator



Jan. 10, 1961 MAGEOCH 2,967,903

STRAIN INSULATOR Filed NOV. 9, 1956 INVENTOR HA RY YALE M AG E CH ATTORNEY.

STRAIN INSULATOR Harry Yale Mageoch, Havertown, Pa., assignor to Electric Service Works, Delta-Star Electric Division, H. K. Porter Company (Delaware), a corporation of Delaware Filed Nov. 9, 1956, Ser. No. 621,346

1 Claim. (Cl. 174-180) This invention relates generally to electric insulator units and more particularly to electric insulator units of the high strain type and a method of manufacturing the same.

A principal object of the present invention is to provide an improved insulator unit capable of withstanding a maximum mechanical load in tension.

Another principal object of the present invention is to provide such a unit the metal components of which are separated by a special insulating compound having high dielectric strength and affording maximum resistance to electrical breakdown.

Still another principal object of the present invention is to provide an improved method for constructing such a unit whereby the metal components of the unit are insulated from one another by one moldable material and jacketed with a different moldable material, these moldable materials being integrally joined together in essentially one operation to conjointly form a single unbroken mass thereof.

Other objects and advantages of the present invention will appear more fully hereinafter, it being understood that the invention consists substantially in the combination, construction, location and relative arrangement of parts, all as described in detail hereinafter, as shown in the accompanying drawings and as finally pointed out in the appended claim.

In the drawings:

Figure 1 is a side view of an insulator unit constructed in accordance with and embodying the principles of the present invention.

Figure 2 is a longitudinal section through the insulator unit shown in Figure 1.

Figure 3 is a transverse section on line 3--3 of Figure 2.

Figure 4 is a partially sectioned side view of the unit of Figure 1 showing each end of the unit fitted with'eyed elements.

Figure 5 is a side view of a modified insulator unit.

Figure 6 is a side view of a second modified insulator unit.

The insulator unit constructed in accordance with and embodying the principles of the present invention includes a socketed member A, a filling B of dielectric material in the socket, a headed member C embedded in the dielectric filling, and an outer jacket D of dielectric material.

Referring particularly to Figure 2, the member A is made of metal and is circular in transverse section throughout its entire length. The base end of this member is in the form of a boss 10 that is provided with an internally threaded central bore 11 which extends a substantial distance into one end thereof, and the opposite end of the member A is in the form of a socket provided with a wall 12 that extends in longitudinal continuation of and in coaxial relation to the boss 10. The socket wall 12 bulges outwardly between the top and base thereof, in consequence of which the socket is of maximum internal diam- ICC eter approximately midway between the rim and bottom of the socket.

The dielectric material B, filling the socket to capacity, is a material that is capable of withstanding high compressive and shear stresses while at the same time having great dielectric strength, for example, wood flour Bakelite.

' This filling B may move within the socket 12, but it will not crack. Instead it will remain intact as a continuous covering around the inner end of the headed member C to thereby secure the insulator unit against electrical breakdown.

The headed member C is made of metal and is circular in transverse section throughout its entire length. The inner end portion of this member C is in the form of a head 13 that is fiaton top and which tapers, as at 14,

axially inwardly and away from the fiat top of the head,

and the opposite end of the member C is in the form of an externally threaded element 15. Intermediate the opposite end portions of the member C, immediately under the tapered head 13 is a main body portion of the member C that tapers, as at 16, axially outwardly and away from the tapered head aforesaid.

The dielectric material D, completely embracing the socketed member A and the headed member B, leaving only the internally threaded end of the boss 10 and the externally threaded element 15 exposed, is an elastic rubber-like material that will stand abuse and resist ultra violet light and weather conditions, for example, rubber base Bakelite.

It is important to observe the following features. The tapered head 13 of the member A is disposed in close spaced relation to the bottom of the socket, and the distance from under the tapered head 13 to the socket rim is substantially greater than one-half the difference between the inside rim diameter of the socket and the diameter of the member A immediately under the tapered head 13. In addition, the inside rim diameter of the socket is sufiicient to permit insertion of the tapered head 13 freely into the socket, and in a transverse section taken immediately under the tapered head 13, the inside diameter of the socket is substantially greater than the inside rim diameter of the socket.

When a load tending to pull the socketed member A and the headed member C apart is applied to the insulator unit, as by means of the eyed elements 17 and 18, Figure 4, the external forces acting upon the unit are translated into compressive forces that act through the tapered head 13 of the member C and the socket wall 12 upon an annular mass of the dielectric filling B that extends about the member C and which intervenes the tapered head 13 and the bulged socket wall 12, and particularly that portion of the latter adjacent the socket rim and opposed to the tapering side of the head 13. In other words, the load is transmitted from one of the members A or C to the other through compression of a mass of dielectric material B between the tapered head 13 of the member C and the bulging socket wall 12 of the member A.

While Figures 1 through 4 illustrate an insulator unit that is male at one end and female at the other, Figure 5 illustrates an insulator unit E that is male at both ends, as at 15 and 19, and fitted with eyed elements, as at 17 and 20, and Figure 6 illustrates an insulator unit F that is female at both ends, as at 21 and 11, and fitted with clevised elements, as at 2222.

In the assembly of the insulator unit, the headed member C is inserted into the socketed member A and is supported in coaxial relation thereto with the head 13 suitably spaced from the base of the socket. The socket is then filled to the brim with the dielectric material B, and next the whole is jacketed with the dielectric material D. It is important to note that these dielectric materials are compatible, i.e., they require essentially the same curing procedure, and in the finished product they conjointly form a single unbroken mass of dielectric material. In effect, these materials B and D are molded. into place in one operation.

It will be understood, of course, that the present invention as hereinbefore described and as shown in the accompanying drawings is susceptible of various changes and modifications which may be made from time to time without departing from the general principles or real spirit of the invention. For example, the member C might not be provided with a head, but instead might be provided with a multiplicity of diamond knurls or axially spaced circumferentially extending external grooves. The socket wall might not be bulged, but instead might be straight and provided with diamond knurls. Accordingly it is intended to claim the same broadly, as well as specifically, as indicated by the appended claim.

What is claimed as new and useful is:

An electric insulator unit comprising a member having at one end thereof a socket with an outwardly bulging sidewall, a filling of dielectric material in said socket, a member having an axially tapered shank and at one end thereof an axially tapered head, said head and part of said shank being disposed within said socket and embedded in said dielectric material, whereby a load tending to pull said members apart is translated into compression of a mass of said dielectric material extending about said headed member and intervening said head and a bulged wall portion of said socket proximate the rim of said socket, the taper of said shank being such that the shank cross-section increases in area in an axial direction from the head end toward the open end of the socket, whereby the tapered shank surface when put in tension is readily separable from the surrounding dielectric to thereby prevent tensile mechanical fracture of the latter and avoid electrical breakdown between said socketed and headed members, the tapers of said head and shank being of opposite sense to one another and the tapered surfaces of said head and shank intersecting one another abruptly where the head joins the shank, said mass of dielectric material thereby being compressed to transmit said tensile load from one to the other of said members, and a jacket of dielectric material commonly embracing said socketed and headed members, said dielectric filling being a material that is oapable of withstanding high compressive and shearing stresses, and said dielectric jacket being a material that is elastic and rubber-like.

References Cited in the file of this patent UNITED STATES PATENTS 488,046 Wirt Dec. 13, 1892 530,498 Ball Dec. 11, 1894 897,700 Ashhaugh Sept. 1, 1908 1,166,391 Steinberger Dec. 28, 1915 1,702,957 Bard Feb. 19, 1929 1,895,738 Shugg et al Jan. 31", 1933' 1,988,155 Bovard Jan. 15, 1935 2,217,229 Morcom Oct. 8', 1940 

